File	Doc	Category	Size	Date	Package
CFBBlockCipher.java	API Doc	Android 1.5 API	7777	Wed May 06 22:41:06 BST 2009	org.bouncycastle.crypto.modes

CFBBlockCipher

• java.lang.Object

Fields Summary
private byte[]	IV
private byte[]	cfbV
private byte[]	cfbOutV
private int	blockSize
private org.bouncycastle.crypto.BlockCipher	cipher
private boolean	encrypting

Constructors Summary

public CFBBlockCipher(org.bouncycastle.crypto.BlockCipher cipher, int bitBlockSize) Basic constructor. param cipher the block cipher to be used as the basis of the feedback mode. param bitBlockSize the block size in bits (note: a multiple of 8) this.cipher = cipher; this.blockSize = bitBlockSize / 8; this.IV = new byte[cipher.getBlockSize()]; this.cfbV = new byte[cipher.getBlockSize()]; this.cfbOutV = new byte[cipher.getBlockSize()];

Methods Summary
public int	decryptBlock(byte[] in, int inOff, byte[] out, int outOff) Do the appropriate processing for CFB mode decryption. param in the array containing the data to be decrypted. param inOff offset into the in array the data starts at. param out the array the encrypted data will be copied into. param outOff the offset into the out array the output will start at. exception DataLengthException if there isn't enough data in in, or space in out. exception IllegalStateException if the cipher isn't initialised. return the number of bytes processed and produced. if ((inOff + blockSize) > in.length) { throw new DataLengthException("input buffer too short"); } if ((outOff + blockSize) > out.length) { throw new DataLengthException("output buffer too short"); } cipher.processBlock(cfbV, 0, cfbOutV, 0); // // change over the input block. // System.arraycopy(cfbV, blockSize, cfbV, 0, cfbV.length - blockSize); System.arraycopy(in, inOff, cfbV, cfbV.length - blockSize, blockSize); // // XOR the cfbV with the plaintext producing the plain text // for (int i = 0; i < blockSize; i++) { out[outOff + i] = (byte)(cfbOutV[i] ^ in[inOff + i]); } return blockSize;
public int	encryptBlock(byte[] in, int inOff, byte[] out, int outOff) Do the appropriate processing for CFB mode encryption. param in the array containing the data to be encrypted. param inOff offset into the in array the data starts at. param out the array the encrypted data will be copied into. param outOff the offset into the out array the output will start at. exception DataLengthException if there isn't enough data in in, or space in out. exception IllegalStateException if the cipher isn't initialised. return the number of bytes processed and produced. if ((inOff + blockSize) > in.length) { throw new DataLengthException("input buffer too short"); } if ((outOff + blockSize) > out.length) { throw new DataLengthException("output buffer too short"); } cipher.processBlock(cfbV, 0, cfbOutV, 0); // // XOR the cfbV with the plaintext producing the cipher text // for (int i = 0; i < blockSize; i++) { out[outOff + i] = (byte)(cfbOutV[i] ^ in[inOff + i]); } // // change over the input block. // System.arraycopy(cfbV, blockSize, cfbV, 0, cfbV.length - blockSize); System.arraycopy(out, outOff, cfbV, cfbV.length - blockSize, blockSize); return blockSize;
public java.lang.String	getAlgorithmName() return the algorithm name and mode. return the name of the underlying algorithm followed by "/CFB" and the block size in bits. return cipher.getAlgorithmName() + "/CFB" + (blockSize * 8);
public int	getBlockSize() return the block size we are operating at. return the block size we are operating at (in bytes). return blockSize;
public org.bouncycastle.crypto.BlockCipher	getUnderlyingCipher() return the underlying block cipher that we are wrapping. return the underlying block cipher that we are wrapping. return cipher;
public void	init(boolean encrypting, org.bouncycastle.crypto.CipherParameters params) Initialise the cipher and, possibly, the initialisation vector (IV). If an IV isn't passed as part of the parameter, the IV will be all zeros. An IV which is too short is handled in FIPS compliant fashion. param encrypting if true the cipher is initialised for encryption, if false for decryption. param params the key and other data required by the cipher. exception IllegalArgumentException if the params argument is inappropriate. this.encrypting = encrypting; if (params instanceof ParametersWithIV) { ParametersWithIV ivParam = (ParametersWithIV)params; byte[] iv = ivParam.getIV(); if (iv.length < IV.length) { // prepend the supplied IV with zeros (per FIPS PUB 81) System.arraycopy(iv, 0, IV, IV.length - iv.length, iv.length); for (int i = 0; i < IV.length - iv.length; i++) { IV[i] = 0; } } else { System.arraycopy(iv, 0, IV, 0, IV.length); } reset(); cipher.init(true, ivParam.getParameters()); } else { reset(); cipher.init(true, params); }
public int	processBlock(byte[] in, int inOff, byte[] out, int outOff) Process one block of input from the array in and write it to the out array. param in the array containing the input data. param inOff offset into the in array the data starts at. param out the array the output data will be copied into. param outOff the offset into the out array the output will start at. exception DataLengthException if there isn't enough data in in, or space in out. exception IllegalStateException if the cipher isn't initialised. return the number of bytes processed and produced. return (encrypting) ? encryptBlock(in, inOff, out, outOff) : decryptBlock(in, inOff, out, outOff);
public void	reset() reset the chaining vector back to the IV and reset the underlying cipher. System.arraycopy(IV, 0, cfbV, 0, IV.length); cipher.reset();